Process of making alkali-metal xanthogenates



Patented July 6, 1926.

4 UNITED STATES EDMUNb C. MISSBACH, OF BERKELEY, CALIFORNIA.

IEBOCESS OF MAKING ALKALI-METAL XANTHOGENATES.

No Drawing.

My invention is a process of making xanthogenates' of alkali-metals,sometimes termed alkali-metal xanthates.

An object of my invention is to form the 5 alkali-metal xanthogenateswithout the usual side reactions experienced in the processes commonlypracticed which render the product im'pure. Another object is to producestable alkali-metal xanthogenates without using water in the process andavoiding the use of solvents or liquids containing water or saltscontaining water of crystallization. 'A further object is to produce aproduct either in crystalline or granular from direct without formationof any mother liquor and in which substantially the only water is thatof one molecule of water of crystallization. Another feature of myinvention is to form a solution of an anhydrous mono-hydric alco- 0 holand carbon bisulfide. This solution may be used with a dry alkali-metalhydroxide in the absence of water.

Previous pr0cesses.Some of the previous processes for makingalkali-metal xanthates 5 use more or less dilute alcohol,carbon-bisulfide,- and an alkali-metal hydroxide with "water, or thealkali-metal hydroxide containing water of crystallization is used and 1the material allowed to react. In these pro- 0 ceduresthe water inintroduced as a dilutent of the alcohol, or as water of crystallizationin the hydroxide or simply added as a sol- ;vent of thealkali-metalhydroxide, and sometimes the water .is added during the 5 course of theprocess.

In these processesv in the presence of water as above mentioned even ifthe reaction mixture is cooled externally or'mixed vwith a suitablevolatile inert compound which does not enter the reaction in order toreduce the speed of such reaction side reactions will take place. Theseside reactions form espe-- ciall sulfo-carbonates (or thio-carbonates ast ey are also termed) in considerable quantities, the'pre'sence of whichis indicated bya more or less dark reddish colored end product and by apeculiar shape of the crystals of the latter and by its distinguishingodor and also by analysis. These alkali-' metal sulfocarbonates as, e.g.

K CS mI-LO Na,CS .H O',

formed in the side re-actions reduce, the

Application filed June 1, 1925. Serial No. 84,177.

purity of the desired alkali-metal xanthogenates sometimes to such anextent as to make the same unfit for many industrial purposes, but theseimpurities also have the tendency to bring about further deteriorationof the alkali-metal xanthogenates and making the latter less stable.For, when alkali-metal xanthogenates are heated in the presence of waterat temperatures from 80 C. upwards will decompose into alcohol,alkali-metal sulfocarbonates, hydrogen sulfide and carbon dioxide. Thesame decomposition will similarly take place although more slowly whenthe alkali-metal xanthogenates are exposed to moist air even at normaltemperatures and the decomposition, moreover,

under these circumstances will be greatly facilitated by the presence ofalkali-metal thiocarbonates.

In some of the prior processes the alcohol used contains at least 7% ofwater by weight, generally considerably more and in addition to thissome procedures add water or utilize the mother liquor originated fromformer operations, which besides its water content has variousimpurities. It has been considered in the past necessary to use anexcess of water to keep the alkali-metal hydroxides in solution untilthe reactions are complete.

It has been recommended to utilize an alcohol of from to volume percent,but

ethyl alcohol of this strength for instance corresponds to a watercontent of the alcohol of from 7.6% to 14.3% by weight. All theseprocesses above mentioned, therefore, favor the formation of largequantities of mother liquor which in turn must be removed from v thealkali-metal xanthogenates crystals, thus causing a considerable loss ofcrystals and at the same time making the process unnecessarily diflicultand expensive.

Another'detriment of the prior recesses is the separation of thecrystals From the mother liquor which are generally removed therefrom bysuction filters or by centrifugal machines with subsequent washin of thecrystals by a suitable volatile liquid agent. By these operations thelaborer is exposed to poisonous and annoying vapors and gases for whichlittle or no protection can be'provided: and also during the handling ofthe wet and unfinished product there is also a danger of irritating skinattacks. The

above mentioned draw-backs do not occur with my process and the workmendo not weights and 'secure as a product practically the full chemicalequivalents thereof. The equation may be expressed as follows: usingethyl alcohol and sodium hydroxide:

canon Neon cs,

46.08 40.01 76.125 nassooointmo; moLw. moLw. mo1.w.

the reactions'being quantitative and the water formed is taken up by thealkalimetal xanthogenate in the form of water of crystallization. I mayuse a number of different monohydric alcohols such bein anhydrous, forinstance, ethyl, methy, butyl alcohol and a number or other alcoholswhich could come in consideration for this purpose. I take advantage ofthe fact that these anhydrous alcohols can now be obtained on the marketin commercial quantities at very moderate prices. These anhydrousalcohols can be mixed with carbon bisulfide to form a solution in anydesired proportion without any separation of either the alcohol or thecarbon bisulfide. Depending on the relative strength these mixtures maybe considered either as a solution of alcohol in carbon bisulfide or asolution'of carbon bisulfide in the alcohol.

These mixtures are very reactive towards alkali-metal hydroxides andwhen these in-- gredients are allowed to react being mixed in theirmolecular proportions: and such reactions are carried out very slowlyunder suflicient cooling and proper stirring, the reaction is completewithout any side reactions. A substantially pure alkali-metalxanthogenate is formed containing only one molecule of water ofcrystallization. The product is very pure and contains onlyapproximately one molecule of water of crystallization. They may be"roduced either in crystalline or a granular orm which may be afterwardspowdered and are very stable. For instance I have found that inutilizing sodium hydroxide with a purity of 98% NaOH havingapproximately2% moisture content I obtain a product corresponding approximately to88% anhydrous sodium .xanthogenate the balance consisting of watercrystallization. The product is substantiall a perfectly dry substanceand may be pow ered as fine as dust, It will not cake nor form intolumps nor deteriorate when stored in air-tight and moisture proofcontainers under normal conditions for a speci cations.

reasonable period. It is suitable for all industrial pur oses wherealkali-metal xanthogenates of ighest purity are required.

Usually alkali-metal xant-hogenates are used for industrial purposes inthe form of comparatively diluted solutions. If an absolutely dry oranhydrous alkali-metal xanthogenate is desired my product either in thecrystalline, ranulated or powder form may be subjecte to a dryingprocedureto remove the water of crystallization. This drying may beaccomplished in a suitable drying apparatus by a current of dry and warmair or an inert gas e. g. nitrogen preferahly under reduced atmosphericpressure andat a temperature below the decomposition point of thecompound.

In the above discussion of my process I have considered all of theingredients on the basis of one hundred percent purity and cor-Commercial application of my process using ethyl alcohol.

In using ethyl alcohol in the anhydrous denatured form sometimesdesignated (ethanol), I utilize 4606 parts by weight which contains4.64% by weight of anhydrous methyl alcohol. This is in accordance withthe U. S. internal revenue special formula No. 1, substituting anhydrousalcohol for 190 roof alcohol as given in the official parts by weight ofpure carbon bisulfide (CS and 4001 parts by weight of pure dry powderedsodium hydroxide (calculated as 100 percent pure and corresponding to4082.6 parts by weight of 98 percent pure NaOH).

In the above reaction methyl alcohol (methanol) forms also alkali-metalxanthogenates similar to the ethyl, alkali-metal xanthogenate whenbrought into reaction with carbon bisulfide and an alkali-metalhydroxide. There is, however, a diiference of the molecular weightbetween ethanol and methanol which should be considered. The molecular,weight of ethanol is 46.06 and that of methanol 32.04.- This shows thataccording to the equation:

c.rI .oH+NaoH+os mssooo n n o a slight excess of methanol would beintro- I With the alcohol I use 7 612.5

in practice it will be negligible. However,

should it be desired to work With strict accuracy, a correction of theWeight of the denatured anhydrous ethyl alcohol could be made veryeasily, for, one part of methanol is equal to 1.4376 parts by weight ofethanol, and one part by weight of ethanol is equal to 0.6956 parts byweight of methanol.

Commercial process using ethyl alcohol and potassimn, hydroxide.

Denatured anhydrous ethyl alcohol and carbon bisulfide in the sameproportions as given above for use with sodium hydroxide butsubstituting potassium hydroxide using the calculated amount of KOH asrequired according to the equation:

Commercial application of process using methyl alcohol.

The procedure is the same as using ethyl alcohol but utilizing 3204'parts by weight of technically pure anhydrous methyl alcohol (methanol)instead for the quantity of denatured anhydrous ethyl alcohol mentionedabove. The pure carbon bisulfide and the pure, dry powered alkalr'metalhydroxide in the proportions indicated in the above formulae.

The ethyl and methyl alcohols may be replaced by any other suitableanhydrous monohydric alcohol, e. g. amyl, butyl alcohols, etc., whichare able to form alkalimetal xanthogenates when allowed to react with analkali-n'ietal hydroxide and carbon bisulfide under proper conditions.

- In the above examples which may be considered as commercial formulaeNos. 1, 2,

and 3 respectively, the manufacture of alkali-metal xanthogenates isperformed without drying, the product so obtained being in granulatedform which may be powdered. If it is desired to obtain crystallineproducts of the same chemical composition, I

use an excess of carbon bisulfide over that given in the above formulae.The excess of'carbon bisulfide which does not re-enter into the reactionmay be driven off 'by raising the temperature somewhat above the boilingpoint of the carbon bisulfide preferably under reduced atmosphericpressure after the formation of the alkali-metal xanthogenatesis'completed and recovering the excess of the carbon bisulfide bycn-(lensing its vapors.

Tcchnz'calz'tz'es of opcmtz'ons.-In carrying out any of my processesabove mentioned I mix the calculated amounts of the anhydrous alcoholand the carbon bisulfide together, cooling the mixture to a lowtemperature preferably below the freezing point of water at normalatmospheric pressure. I have found a temperature of about zero C. issatisfactory. This cooled solution of the anhydrous alcohol and thecarbon bisulfide is very-slowly added to the proper molecularproportions of a dry finely ground or powdered alkali-metal hydroxide.This is preferably done in a closed vessel provided with an efiicientmixing, kneadin and triturating or a kneading and grind: ing devicecombined. The apparatus must also be provided with a reflux condenser, athermometer and a cooling device, the latter of which may be utilized orconverted into a heating device at will. The reflux condenser should beflexible in order that the same could be used as an ordinary condenserif it were desired to remove the condensed carbon bisulfide vapor fromthe reaction vessel in case an excess of carbon bisulfide had been usedfor the manufacture of crystalline alkali-metal xanthogenates. In theremoval of the excess CS which may be done as above described byremoving it from the finished product at reduced atmospheric pressureand without raising the temperature above C.

The.temperature of the reaction mixture must be regulated and preferablynot allowed to rise above 40 C. and not below 30 C. until the reactionsare completed,

when the product may be discharged directly into the containers in whichit may be stored and shipped.

It will thus be seen that my process for the manufacture of purealkali-metal xanthogenates in either lumps, granular, or powderedorcrystalline form is extremely simple that it may be carried out inasingle, simple but specially constructed apparatus which requires theattention of only one operator, therefore saving considerable amount oflabor. The process requires no crystallizers, centrifugals, or otherliquor removing devices which are not only very important, time saving,but also money saving factors.

Formation of a stable solution of an anhyclrous monohyalrz'o alcohol andcarbon bisulfide.

An important sub-step in my complete process is-the formation of astable. mixture or solution of anhydrous monohydric alcohol in carbonbisulfide or vice versa in molecular proportion or in proportions withthe carbon'bisulfide in excess of the proportion of the anhydrousmonohydric alcohol. With the mixtures or solutions I prepare it can beshipped by railroad without material danger and the mixture utilized atits destination for. forming alkali-- metal xantho enates. It is Wellknown that pure carbon isulfide itself is a dangerous chemical to shipbut my solution has a much higher boiling point,'is less inflammable andis not subject to static electric charges, as is the case with purecarbon bisulfide thereby reducing the danger of explosions and ignitionof the liquid by electric sparks. V

I have ascertained that carbon blsulfide and an anhydrous monohydricalcohol (e. ethyl, methyl, or butyl alcohol) Wlll. dissolve in each oter in any desired proportion. These solutions may be called either anal- .coholic solution of carbon bisulfide or a-solution of the alcoholin carbon bisulfide. If, however, the alcohol contains water thesolubility of carbon bisulfide in diluted monohydric alcohols decreasesconsiderably and the solubility of a diluted monohydric alcohol incarbon bisulfide may become so low, that for practical purposes it wouldbe negligible. For example, denatured ethyl alcohol of 95 volume percent(which contains 92.42 percent alcohol by weight with 7.68% water) in theproportions of 54 to 55 parts by weight, will dissolve only from 45 to46-parts by weight of pure carbon bisulfide at normal temperature, thevariat-ion of proportions of dissolved carbon bisulfide depending on thenature and the quantity of the denaturant present in the alcohol.Whereas only a fraction of one percent of denatured ethyl alcohol at thesame strength will be soluble in pure carbon bisulfide.

It will thus be seen that by using 311,311, hydrous monohydric alcohol Iobtain an anhydrous solution of the alcohol and carbon bisulfide in theproportions required by the formulae to produce an alkali-metalhydroxide the xanthogenates thereof, or I may readily obtain a solutionhaving a much greater or lesser proportion ofcarbon bisul- Having claimis:

1. The method of producing alkali-metal xanthogenates consisting incausing a reaction of a solution of an anhydrous monohydrlc alcohol incarbon bisulfide on a dry alkali-metal hydroxide the alcohol and thealkali-metal hydroxide being used in molecular proportions.

2. The method of producing alkali-metal xanthogenates consisting incausing a reaction of a monohydric alcohol with carbon bisulfide on adry alkali-metal hydroxide in which no water or any other substancecontaining water is used to dilute the reaction mixture.

3. The method of producing alkali-metal xanthogentates as claimed inclaim 1, in which all three of the ingredients are utilized in theproportions of their molecular weights. 4. The method of producingalkali-metal xanthogenates comprising forming a solution of ananhydrous'monohydric alcohol describedmy invention, what I with carbonbisulfide and causing a reaction of the solution on a dry alkali-metalhydroxide.

5. The method of producing alkali-metal xanthogenates comprising forminga, solution of an anhydrous monohydric' alcohol with carbon bisulfideand causing a reaction of the solution on a dry alkali-metal hydrox ide,in which no water or any other substance containing water is utilized asa dilutent.

6. The method of claim 4 in which ingredients are utilized in theproportion of their molecular weights.

7. The method of claim 4 comprising cooling the solution of theanhydrous monohydric alcoholand carbon bisulfide and adding the solutionslowly to the dry alkalimetal hydroxide and cooling and agitating themixture during the reaction.

8. The process combining an anhydrous monohydric alcohol, carbonbisulfide and a dry, finely crushed, or powered alkali-metal hydroxideto form a solid, pure granulated alkali-metal xanthogenate in a singleoperation without the formation of a mother liquor and in. which theproduct can be powdered without previous drying.

9. The process as claimed in claim 8 in which an excess amount of carbonbisulfide is used to form a more perfect crystalline product whichcontains only water in the form of one molecule of water ofcrystallization and further removing the excess of carbon bisulfide fromthe product.

' 10. The process as claimed in'claim 8, in which an excess amount ofcarbon bisulfide is used which is afterwards removed from the product bycondensing the carbon bisulfide vapor from the reaction vessel at apressure below atmospheric and without raising the temperature above 30C. a

11. The process of making alkali-metal xanthogenates comprising reactingan anhydrous monohydric alcohol, carbon bisulfide and an alkali-metalhydroxide in substantially the proportions of their molecular weights toform directly a crystalline or granular product containing water only'in the form of water of crystallization.

12. The method of claim 11 comprising in addition drying the product toremove the water of crystallization.

13. The method of claim 11 comprising in addition drying the product toremove the waterof crystallization under pressure less than atmosphericand at a temperature below the decomposition point of the compound. I

14. The process of making'substantially dry alkali-metal xanthogenatescomprising making a solution of an anhydrous monohydric alcohol in theproportion of its molecular weight .with carbon bisulfide in theproportion of 7 6.125 parts by weight, coolin the solution-and mixing itslowly with so ium hydroxide of 98% purity in the proportion of 40.83parts by weight, said sodium hydroxide being substantially dry andground or pulverized, and cooling and stirring the ingredients duringthe reaction.

15. The method of making alkali-metal xanthogenates conprising utilizing4606 parts by weight commercial denatured anhydrous ethyl alcoholcontaining substantiall 4.64% by weight of anhydrous methyl alco 01 and95.36% of ethyl alcohol utilizing therewith pure carbon bisulfide in theproportion of substantially 7612.5 parts by weight and reacting thesewith pure dry powdered sodium hydroxide of substantially purity, in theproportion of 4082.6 parts weight. g 16. T e manufacture of analkali-metal xanthogenate as a direct product without the formation of.mother liquor having water only in the form of water of crystallization.

17. As a direct product an alkali-metal xanthogenate formed without theuse of diluent water and without the formation of any mother liquor suchproduct being crystalline or granular and having a water content onl inthe form' of. one molecule of water 0 crystallization. v

18. A solution for forming alkali-metal xanthogenates from dry powderedalkalimetal hydroxides consisting of an anhydrousmonohydric alcohol andcarbon bisulfide with the carbon bisulfide being in direct proportion tothe alcohol in accordance with their molecular weights, such solutionbeing stable and having a higher boiling point than carbon bisulfide.

In testimony whereof I afiix my signature.

EDMUND C. MISSBACH.

